Microsoft's Internet Explorer, which has dominated the Web browser market since blowing by Netscape in the late 1990s, last month fell below the 50% market share level for the first time in years.

IE's share of the worldwide market fell to 49.87% in September, down from 51.3% in August and 58.4% a year ago. It is followed by Firefox, which increased its share slightly from 30.09% to 31.5% and Google Chrome, which grabbed 11.54% share, more than triple its September 2009 share, according to market watcher StatCounter.

"This is certainly a milestone in the Internet browser wars," said Aodhan Cullen, CEO of StatCounter, in a statement. "Just two years ago IE dominated the worldwide market with 67%."Back in 2002, IE had more than a 90% share in the wake of operating system/Web browser bundling that got the Department of Justice's attention in the form of an antitrust lawsuit.

A suit settled last year between Microsoft and the European Union over a lack of browser choice might have helped knock IE below the 50% mark, according to Cullen. In Europe, IE holds a 40.26% share, down from 46.44% last September.

While web browser advances were few and far between a decade ago, competition among IE, Firefox, Chrome, Apple Safari and Opera has fueled new developments, including increasingly faster browsers. IE 9, now in beta, has been impressing reviewers with its speed.

StatCounter bases its numbers on data collected across 15 billion page views per month from 3 million Websites.